Every iPhone comes with an identification number -- like a serial number – that’s used for connecting data to a specific handset. Until recently, the UDID allowed developers and marketers to track activity on the phone, such as app purchases, game scores for Game Center, delivering push messages, or any other activity unique to that iPhone.

Recently, Apple announced that it would be replacing its UDID with a new, improved Identifier for Advertising (also called IDFA or sometimes IFA) for IOS6. Its arrival brings about some major changes to advertising on iOS:

Advertising IDs are no longer tied to a user’s device and are thus no longer permanent. This means users are now able to reset their identifier whenever they wish.

Users are now also able to opt out of behaviorally targeted advertising completely via their phone settings.

This will have benefits for users, developers, and the industry at large. However, although IDFA is out and available, there are still a few limitations that need to be examined and addressed before the rollout achieves 100% adoption and can be considered a success.

Here’s where Apple needs to focus next to ensure the success of the new Identifier for Advertising:

1. Allow for more robust user controls beyond just opting in or out

Currently, users can choose only whether to opt in or out of behavioral advertising. While this is a great first step toward improved user privacy controls, Apple should give users even more granular control.

One way Apple can do this is to create a more user-friendly version of Google's “Ad Preference Center,” which allows users to not only opt in and out of behavioral advertising on the web, but also view – and choose – which interest-based ad categories they will receive. For instance, using Google’s Ad Preference Center, a user could perhaps see that, based on his or her browsing history, he or she is currently categorized as a sports enthusiast, car aficionado, and a potential purchaser of real estate. If the user decides this is inaccurate or doesn’t want to receive ads in these categories any longer, he/she can choose which of the categories to opt out of – and even choose to opt into another category altogether if the user wishes to receive ads related to, say, travel. I would love to see Apple allow this degree of control for users on mobile in the future, as this benefits both advertisers and users alike.

2. Ensure there are no outstanding bugs

With the new iOS rollout, a bug was uncovered where any user who updated over Wi-Fi showed IDs as all zeros, instead of the unique number sequences being sent by those who plugged their devices in and updated via iTunes or Xcode. Apple will need to ensure that there are no outstanding bugs in the IDFA system to ensure smooth adoption and transition from UDID to IDFA.

3. Encourage wider adoption

Since the new Identifier for Advertising is only available on iOS6, users on previous OS versions won’t be tracked with IDFA and will still be on the old UDID system. Our own first-party data shows that users have adopted iOS6 122% more quickly than iOS 5 after 2 days, with around 20% adoption by Day 2. To get the remaining 80% or so of users on board, Apple will need to fix common user complaints on iOS6 to increase adoption – for instance, a significant number of users have chosen not to update their OS due to issues with the new maps interface and other complaints. Additionally, Apple may need to provide further incentives to developers to make the update or simplify the app submission process, since re-submitting an app to the app store can often be a tedious and time-consuming review process.

Although the launch of Apple’s new Identifier for Advertising is a big step forward, there’s still a long way to go before user behavior identifiers and user privacy controls on mobile catch up to their web counterparts. It will be interesting to see what Apple does next, and we hope to see continued support, improvements, and wider adoption of the new IDFA.